The present invention relates to a rocker arm made of sheet metal for a valve mechanism of an automobile engine, and a method of manufacturing the same.
The rocker arm furnished to the valve mechanism of the automobile engine is provided with a body made of sheet metal, a roller disposed between side walls of the body, and an axis for rotatably supporting the roller via needle rollers. The axis is non-rotatably inserted in axial holes formed in the side walls of the body. A rotation of cam in contact with the roller oscillates the body, and the valve stem is vertically moved in cooperation with this oscillation to open and close a valve (see, for example, Patent Laid Open No. 2001-55912).
The body of the rocker arm receives load from the cam via the roller. In particular, the surrounds of the axial holes through which the axis passing through the body is inserted receives large load. Therefore, for securing rigidity in response to load, the sheet metal having thickness durable against the load is employed for the material of the body, so that the weight of the rocker arm increases by such an amount of the durable thickness.
Further, in general, the axial holes are formed by punching the sheet metal by an amount of the diameter of the axis, and punched circular parts are scrapped as they are, resulting in lowering yield rate.